Process of vulcanizing rubber and product thereof



blacks are present ornot.

Patented Sept. 11, 1951 assmsss. f

rnocsssior IVUIZGANIZlKG RUBBER AND I, THEREOF -William- McGillivray Morgan, Oswestry, England, {I lassignor to l=Monsanto Chemical Company, .St.

. Louis, Mo .a,.;co.rporation' of Delaware No Drawing. "Application December "16,--1949;-Se-

' "riaPNo; 133,485. "fIn Great Britain December j 'Th-is invention relatesto the processing. of rubf b'e'r. and I to new vulcanization-'retarders.

iicla m. (cit- 266482 The' use of a vulcanization retarder in thecom- :pounding of I rubber-is common practice in order 'to r'educethe tendency to '--scorch, which can "be definedas partialand prematurevulcaniza'r tion of theru bberstock taking place during the mix-ing operation in the course of which the filler, as for example-carbon black, and vulcanization aocelerator, among-other substances, areintro- "duced, I or during the shaping operation, extru- *sion or calendering for example. -The-use-of *v'ulcanization retarders may, moreover,-become pf-increasing importance-with the greater use of these-called furnace carbon blacks. In the process of mixing rubber carbon blacks madeby the channel process-(the so-ca-lled channel car- "bon blacks) are in wide use, especially in'the tire industry, and carbon blacks made by the furnace process (known as furnace carbon-blacks) are also in-considerable use; Howeverythere is a possibility that furnace ca'rbonblacksmay become *more widely used than they are-at present, "and it has'been' found that when 'using' furnace blacks there is a greater tendency-for scorching to take place during compounding. Thisfitend- *ency appears to increasewitlrthe'finenessof'the furnace black. I

"'I have now discovered anew series. of vulcanization retarders, particularly usefulfin ruboer stocks containing furnace 'carbon blacks, but also useful in other instances whether carbon According to the invention thereisenfployed as vulcanization retarde'r an organic hydrogen sulphate or a salt of such a 'compound witha metal "other than an alkali metahformd' of course lbyvreplacement of the availablehyditogen in the hydrogen sulphate group.

Preferably the organic hydrogen sulphate is an aliphatic hydrogen sulphate, especially a longcha'in'aliphatic' compound, and it is desirable that the aliphatic group shou-ldcontain'a carbon chain of not less than eight carbon atoms. The lauryl a-nd' -oleyl groups "are'eminently suitable. An-

other hydrogen sulphate which has beenfound particularly valuableltespecially when used in the formof its zinc salt) is one-which canbenbstained by sulphating a commercial aliphaticsecl ondaryalcohol of the formula The zinc salts have been found to be especially effective, and other particularly suitable examples are the aluminum and calcium salts.

wherelRis'an aliphatic chain hailing se age I length often carbon atoms.

'The .inventlonis-illustrated by the following examples relating :to the treatment -,of. ;natural rubber, to which the invention primarily relates. It will be appreciated, however, that it is also useful iin -vulcanizing synthetic rubbers 'JTGf the i type which can be vulcanized with sulphur.

Example 1 Zinc. lauryl: sulphate inra quantity of 2. parts by weight was added during the "mixingzof the tie!- lowing stock, using a'very. fine particle size furnace carbon black:

Par-ts by weight -Smoked sheets-"rubber R Carbon black 45- -Zinc'oxide z 5 Stea'ric acid l 53' Portions oflthis stock/and. ,one identical except thatitwas .compounded withoutithe addition of the zinc: lauryl sulphate were tested "for .scorchingproperties using a Mooney plastometer (with a large rotor) at C., oneminutespreheating of the stock being given in the apparatus prior to starting the -motor. In this way the Mooney plasticity-value was obtained for-each stock'after different periods of heating,---andz1 hence the decrease in the plasticity'of the stockwtth increased time of heating could be determined. I A decrease in theplasticityqis indicated by increase in -the Mooney plasticity-value.

The following results were obtained:

The curves that can be drawn for the two stocks by plotting the Mooney plasticity value each example;

"231E zinc lauryl time might be taken as the time required for"; I

the Mooney plasticity value to rise to 5.0 units stock, both points being determined fr'orri'th'e" graph. a

In the above instance, the =fscorclrtime for the base stock measured in this way-Was 12% minutes, and that for the stock containing the I zinc salt was minutes;

The zinc lauryl sulphate used inthis eicample was prepared by sulphating lauryl alcohol to give lauryl hydrogen sulphate and reacting this with zinc chloride to for'r-n the zinc salt, and the salts used in the'fur ther examples given below were obtained' in an analogous manner.

'1. Example 2 .TExample. 1 .was repeated using 0.8 part by weightof zinc .oleyl sulphate instead of the 2 parts of zinc lauryl sulphate.

The scorch time of the base stock was found to -be-12 minutes, andthatof the stock containing the zinc salt was found to be 15 minutes.

:..'.Example 1 was repeated using 2 parts by Weight of aluminum oleyl sulphate instead of the 2 parts of zinc lauryl Sulphate,

2,567,858 ii 7:1. i521};

eighteen carbon atoms and zinc, calcium and aluminum salts thereof.

2; A process .of vulcanizing a furnace black rubber stock which comprises lieating.; the rubber containing a furnace black, sulfur and a .thiazole accelerator in the presence of a small I V amount of a vulcanization retarder selected from above the minimum value given in the test by the ,5

the group consisting of aliphatic hydrogen sulfates'containing at least eight but not more than eighteen carbon atoms and zinc, calcium and aluminum salts thereof.

3. .A process of vulcanizing a rubber which comprises heating the rubber containing sulfur and an organic accelerator in the presence of a small .jThe, scorchtime of the base stockwas found to be M minutes. and, that of the stock containing the aluminum salt wasfound to be 16 /2 minutes. :It; is to be observed that the difference between $11 fingers obtained with the base stock in this,.

present example and in Example 1 is due to the fact that the two stocks were prepared on different goccasions. Divergences of this kind are common jin rubber technology, but the respective figures for the base stock 'provide'proper comparison in Example l was repeated using 2 parts by weight of calcium oleyl sulphate instead of the 2' parts sulphate. p i 'The' scorch time of thebase stock was found I to be 13 minutes, and that of the stock containing the c'alciumisalt was found to be 16 'minutes.

" Example 5 I Example 1 wasi repeated using, instead of the? parts by weight of zinc lauryl sulphate, a similar -weight of the zinc salt of the hydrogen sulphate .of a commercial? aliphatic secondary alcohol of thetformula Ramon) .CHs

'where R was an {aliphatic chain having an average length of ten carbon atoms.

'The scorch time of the base stock was found to be 12 minutes, and that of the stock containing the zinc salt was found to be 21' minutes.

What is claimed is:-

1. A process of vulcanizing'a rubber. which com prises heating the rubber containing sulfur and" an organic accelerator in the presence'or a small process of claim 3.

process of claim 5.

,"The followingreferences are of record amount of a vulcanization retarder consisting essentially in a. zinc salt of an aliphatic hydrogen sulfate containing at least eight but not more than eighteen carbon atoms. .14. A process of vulcanizing a rubber which comprises heating the rubber containing sulfur and an organic accelerator in the presence of a small amount of a vulcanization retarder consisting es sentially in the hydrogen sulfate of an alcohol-of the structure R.CH(OH) .CHs where R isan aliphatic chain having ten carbon atoms. 5. A process of vulcanizing a rubber which comprises heating the rubber containing sulfur and an organic accelerator in the presence of a small amount of a vulcanization retarder consisting es sentially in a zinc salt of the hydrogen sulfategof an alcohol of the structure R.CH(OH) .CH; where R is an aliphatic chain having ten carbon atoms. e 6. A process of vulcanizing a rubber which comprises heating the rubber containing sulfur and an organic accelerator in the presence of a small .amount-ofa vulcanization retarder consisting essentially in a zinc salt of the hydrogen sulfate of oleyl alcohol. 1

7-. A process of vulcanizing a rubber which comprises. heating the rubber containing sulfurand an organic accelerator in the presence of a small amount of a vulcanization retarder consistingessentially. in a zinc salt of the hydrogen sulfate of laurylalcohol. a 8. Rubber which has been vulcanized by the process of claim 1.

. 9. Rubber which has been vulcanizedby the process ofclaim 2.

10. Rubber which hasbeen vulcanizedby the 11. Rubber which has been vulcanized by the process of claim 4. I 12. Rubber which has been vulcanized by the '13. Rubber which has been vulcanized by,tlie process of claim 6. V

14. Rubber which has been vulcanize 'by"the process of claim '7. I

'WILLIAM MGGILLIVRAY MORGAR- REFERENCES CITED in the ,iileof this patent:

UNITED STATES PATENTS Number V 7 Name Date 1,844,943 Cadwell Feb. 16,1932 1,871,037 Cadwell Aug. 9, 1932 2,046,015 Bunbury et a1 June 30, 1936 v 2,058,840 Thies Oct. 27, 1936 Williams Nov. 30 19,37 

1. A PROCESS FOR VULCANIZING A RUBBER WHICH COMPRISES HEATING THE RUBBER CONTAINING SULFUR AND AN ORGANIC ACCELERATOR IN THE PRESENCE OF A SMALL AMOUNT OF A VULCANIZATION RETARDER SELECTED FROM THE GROUP CONSISTING OF ALIPHATIC HYDROGEN SULFATES CONTAINING AT LEAST EIGHT BUT NOT MORE THAN EIGHTEEN CARBON ATOMS AND ZINC, CALCIUM AND ALUMINUM SALTS THEREOF. 